Method for decreasing a concentration of metal in aqueous solution

Abstract

A method and system for decreasing the concentration of at least one metal in an aqueous solution. The metal may be molybdenum, tungsten, or both. An aqueous solution is introduced into at least one reaction zone, and at least one source of hydroxide ions is provided into the at least one reaction zone in an amount sufficient to precipitate at least some of the mass of the at least one metal. The aqueous solution includes a mass of the at least one metal and a mass of at least one reducing agent. The at least one reducing agent includes at least ferrous iron from at least one source of the at least one reducing agent. A composition of tungsten ferrite or molybdenum tungsten ferrite may be formed. The method may be used for purifying water, for the refining of metals, or to facilitate a chemical analytical determination.

1. A method comprising:
 a) providing an aqueous solution into at least one reaction zone, said aqueous solution comprising:
 i) tungsten; and 
 ii) at least one reducing agent comprising ferrous iron, and the ferrous iron comprises ferrous chloride or metallic iron; and 
 
 b) providing hydroxide ions into the reaction zone in an amount sufficient to precipitate at least some of the tungsten in the form of tungsten ferrite, and thereby decreasing the concentration of the tungsten in the aqueous solution, wherein the mass of said ferrous iron provided to said at least one reaction zone is at least about 1.5 times the mass of said tungsten, and wherein said at least one reaction zone is maintained at a pH in the range from about 6 to about 14. 
 
     
     
       2. The method of  claim 1 , wherein the mass of said ferrous iron provided to said at least one reaction zone is at least about three times the mass of said tungsten. 
     
     
       3. The method of  claim 1 , wherein said at least one reaction zone is maintained at a temperature in a range from about 0° C. to about 100° C. 
     
     
       4. The method of  claim 1 , wherein said at least one reaction zone is in at least one reactor selected from a group consisting of a continuous tank reactor, a continuous tubular reactor, and a batch reactor. 
     
     
       5. The method of  claim 1 , wherein said hydroxide ions are derived from a material that is selected from a group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, calcium carbonate, and potassium carbonate. 
     
     
       6. The method of  claim 5 , wherein the hydroxide ions are derived from sodium hydroxide. 
     
     
       7. The method of  claim 5 , wherein the hydroxide ions are derived from potassium hydroxide. 
     
     
       8. The method of  claim 5 , wherein the hydroxide ions are derived from magnesium hydroxide. 
     
     
       9. The method of  claim 5 , wherein the hydroxide ions are derived from calcium hydroxide. 
     
     
       10. The method of  claim 5 , wherein the hydroxide ions are derived from magnesium oxide. 
     
     
       11. The method of  claim 5 , wherein the hydroxide ions are derived from calcium oxide. 
     
     
       12. The method of  claim 5 , wherein the hydroxide ions are derived from calcium carbonate. 
     
     
       13. The method of  claim 5 , wherein the hydroxide ions are derived from potassium carbonate. 
     
     
       14. The method of  claim 1 , further comprising recovering at least some of said tungsten ferrite. 
     
     
       15. The method of  claim 14 , wherein recovering comprises settling, filtering, centrifuging, or magnetically separating. 
     
     
       16. The method of  claim 1 , wherein the decreasing of the concentration is to an amount such that up to 98 percent of the tungsten is removed from the aqueous solution. 
     
     
       17. The method of  claim 1 , wherein the decreasing of the concentration of the tungsten in the aqueous solution refines the tungsten. 
     
     
       18. The method of  claim 1 , wherein the ferrous iron comprises ferrous chloride. 
     
     
       19. The method of  claim 1 , wherein the ferrous iron comprises metallic iron. 
     
     
       20. The method of  claim 1 , wherein the reaction zone is maintained at a pH of about 8.5.